1. Field of the Invention
The present invention relates to a stage device and an exposure apparatus. More particularly, the present invention relates to a stage device including two stages, which hold two objects, and an exposure apparatus, which includes the stage device.
2. Description of the Related Art
Conventionally, in a lithographic process to manufacture devices such as semiconductors and liquid crystal displays, various types of exposure apparatus have been used to transfer patterns formed on a mask or a reticle (to be generically referred to as a xe2x80x9creticlexe2x80x9d hereinafter) onto a substrate such as a wafer or a glass plate (to be generically referred to as a xe2x80x9cwaferxe2x80x9d hereinafter) coated with a resist or the like. In recent years, a projection exposure apparatus based on a step-and-repeat method (a so-called stepper) and a scanning type projection exposure apparatus based on a step-and-scan method (a so-called scanning stepper) have been mainly used.
With an exposure apparatus such as the stepper, since the wafer must be accurately positioned to a projection position of a reticle pattern, the wafer is held on a wafer holder by vacuum chucking, and the wafer holder is fixed on a wafer table.
In the process performed by the exposure apparatus such as the stepper, after the wafer loading process to load a wafer onto the wafer stage by using the wafer loader, the alignment process to measure the position of each shot area on the wafer is performed. This alignment process, in general, includes: the search alignment process which is performed based on the outer shape of a wafer or by detecting search alignment marks on the wafer; and the fine alignment process which is performed following the search alignment process to accurately obtain the position of each shot area on the wafer. For this fine alignment process, the EGA (Enhanced Global Alignment) method disclosed in, for example, U.S. Pat. Nos. 4,780,617 and 4,962,318 is used. With this method, a plurality of sample shots within a wafer are selected in advance, and the position of alignment marks (wafer marks) with respect to the sample shots are sequentially measured. The array data of all the shots on the wafer are then obtained by performing statistical calculation based on a so-called least-squares method based on the measurement results and the shot array designed values. According to this method, the coordinate position of each shot area can be obtained relatively accurately with a high throughput.
Next, the respective shot areas on the wafer are sequentially positioned based on the coordinate positions of the respective shot areas obtained by the EGA method or the like and a baseline amount measured in advance. Then, the exposure process is performed to transfer the reticle pattern image onto the wafer through the projection optical system. After the exposure process, the wafer unloading process to unload the wafer having completed exposure from the wafer stage by using the wafer unloader is performed. The wafer unloading process constitutes the wafer exchanging process, along with the wafer loading process in which the wafer is exposed. The exposure apparatus, when focusing on each wafer, sequentially repeats three main operations, i.e., wafer exchange, alignment, and exposure. In the case the exposure apparatus performs these process by using one wafer table, TT is the processing time per wafer, T1 is the wafer exchange time, T2 is the alignment time, and T3 is exposure time, therefore:
TT=T1+T2+T3xe2x80x83xe2x80x83(1)
The wafer exchange time T1 is shorter than the alignment time T2 and exposure time T3. Most of the processing time TT per wafer is taken up by the alignment T2 and exposure time T3.
Exposure apparatus such as steppers are apparatus that mass-produce semiconductor devices and the like, therefore inevitably require an improvement in productivity (throughput). In order to meet such a requirement, an exposure apparatus which concurrently performs the alignment and exposure process by using two substrate tables, while incorporating resources to independently drive the tables, has been proposed in, for example, Japan Patent Laid Open No. 10-214783 (to be referred to as a xe2x80x9cprior artxe2x80x9d hereinafter). with this apparatus, the processing time TT xe2x80x2 is as follows:
TTxe2x80x2=MAX[T1+T2, T3]xe2x80x83xe2x80x83(2)
That is, the throughput greatly improves compared with the case in which only one substrate table is used.
Recently, when producing semiconductor devices, in order to improve the productivity, the size of the wafer tends to gradually increase from 6 inches to 8 and 12 inches. And the wafer stage, which has also increased in size, requires to be driven with a higher speed. That is, as the wafer stage increases in weight, the driving force of the wafer stage needs to be further increased. An increase in the weight of the wafer stage causes the center of gravity to move more frequently in a stage device including the wafer stage, along with the movement of the wafer stage. This causes the exposure apparatus including the stage device to lose its stability, and will lead to deformation of the exposure apparatus. Also, for example, when the wafer stage performs reciprocal movements, vibration is caused in the overall exposure apparatus.
And, if the wafer stage is driven with a large force, the reaction force causes the overall exposure apparatus to deform or to vibrate.
Further, the above conventional technique is an excellent technique to improve the throughput. However, when considering the increase in the size and weight of each wafer stage, and the two wafer stages being independently driven with large driving forces corresponding to the respective stages, the exposure apparatus may further deform and vibrate compared to the exposure apparatus with one wafer stage.
As the degree of integration of semiconductor devices increases, the device rule (practical minimum line width) decreases every year, and an improvement in pattern transfer precision is thus required. In spite of such a requirement for an improvement in pattern transfer precision, the above deformation and vibration of the exposure apparatus act as factors that cause a deterioration in pattern transfer precision. In other words, it is becoming difficult to satisfy both the requirements for an improvement in pattern transfer precision and an improvement in throughput.
The present invention has been made in consideration of this situation, and has as its first object to provide a new stage device which independently drives two stages, while reducing the influence of the center of gravity shifting caused by the stages being driven and vibration caused by the reaction force.
It is the second object of the present invention to provide an exposure apparatus that can improve the throughput while improving the precision of pattern transfer.
According to the first aspect of the present invention, there is provided a stage device comprising: a first and second stage movably supported on a base; and a moving member which is movably supported on the base and moves to cancel out a shift in a center of gravity of the stage device when at least one of the first and second stages move. The term xe2x80x9ccanceling out a shift in a center of gravityxe2x80x9d includes completely canceling out a shift in the center of gravity as well as partially canceling out a shift in the center of gravity, i.e., reducing the amount of the center of gravity position moving.
According to this arrangement, the center of the gravity of the stage device moves when at least one of the first and second stage moves. However, this is canceled out by moving the moving member. That is, the shift in the center of gravity of the stage device when at least one of the first and second stage moves can be prevented. This makes it possible to prevent the external members from losing stability when compared with the initial state of the stage device.
The stage device of the present invention can further comprise a base supporting member which movably supports the base. In this case, the shift in the center of gravity of the stage device, which cannot be completely canceled out by moving the moving member, can be completely canceled out by moving the base.
With the stage device of the present invention, on driving the first stage, second stage, or moving member, the device can be structured so that the first stage, second stage or moving member is driven with respect to the base. And the reaction force generated by the driving acts on the base. In this case, the base can be structured so that it moves on the base supporting member by a resultant of forces of a reaction force generated when at least one of the first and second stage moves, and a reaction force generated when the moving member moves. With this arrangement, the friction between the base and the base support member is reduced, thus preventing the shift in the center of gravity of the stage device.
The stage device of the present invention can further comprise a structure of a plurality of mass bodies capable of moving independently. In such a case, by adjusting the movement of the plurality of mass bodies according to the movement of the first or second stage, the shift in the center of gravity of the stage device can be canceled out. Also, if the stage device is structured so that the reaction force is to act on the base when the first stage, second stage, or moving member is driven, the sum of reaction forces acting on the base can be reduced to almost 0. This can be achieved, by adjusting the driving force of the plurality of mass bodies in consideration of the driving force of the first stage or second stage and its positional relationship with the base, and positional relationship between the plurality of mass bodies and the base.
If friction between the first stage, the second stage, and the respective plurality of mass bodies and the base is sufficiently small, the shift in the center of gravity of the stage device and the reaction force acting on the base can be cancelled all at once. As a method to support the first stage and second stage and the plurality of mass bodies with a base, by a sufficiently small frictional force, a method such as an air levitation method or a magnetic levitation method is available.
In the case the first and second stages and the plurality of mass bodies move two-dimensionally along a predetermined moving plane, and the respective mass bodies can be driven in any two-dimensional directions, the shift in the center of gravity of the stage device can be canceled out when the number of mass bodies is two or more. Also, in the case the base is structured so that the reaction force act when driving the first stage, the second stage, or the moving member, the sum of reaction forces acting as a two-dimensional translation force in a direction parallel to a predetermined moving plane or two-dimensional rotational forces can be reduced to almost 0. In addition, if the reaction force acting on the base when driving the first stage, second stage, and the plurality of mass bodies are flush, the sum of reaction forces including three-dimensional rotational forces can be reduced to 0.
Also, when the first stage, the second stage, and the plurality of mass bodies move along a predetermined moving plane two-dimensionally, and the plurality of mass bodies are driven in directions which are not all parallel to one another, if three or more mass bodies are used, then the shift in the center of gravity of the stage device can be canceled out. And, in the case the base is structured so that the reaction force act when driving the first stage, the second stage, or the moving member, the sum of reaction forces acting as a two-dimensional translation force in a direction parallel to a predetermined moving plane or two-dimensional rotational forces can be reduced to almost 0. In addition, if the reaction force acting on the base when driving the first stage, second stage, and the plurality of mass bodies are flush, the sum of reaction forces including three-dimensional rotational forces can be reduced to 0.
The stage device of the present invention can have the structure of further comprising a first driving unit which includes a first mover fixed to the first stage and a first stator fixed to the base, the first driving unit driving the first mover by electromagnetic interaction; and a second driving unit which includes a second mover fixed to the second stage and a second stator fixed to the base, the second driving unit driving the second mover by electromagnetic interaction. In such a case, the first stage and the second stage can be moved at a high speed with high controllability. In the case planar motors are used as the first driving unit and second driving unit, the first stator and second stator can be integrated into one unit.
The stage device of the present invention can further comprise a third driving unit which includes a third mover fixed to the moving member and a third stator fixed to the base, the third driving unit driving the third mover by electromagnetic interaction. In such a case, the moving member can be controlled at a high speed with high controllability. If the moving member includes a plurality of mass bodies which can be independently driven, the third mover includes movers equal in number to the mass bodies, and the second stators include stators equal in number to the mass bodies. In the case a planar motor is used as the third driving unit. In this case, even if the moving member includes a plurality of mass bodies which can be independently driven, all the stators can be of an integrated structure.
Furthermore, in the case planar motors are used as the first, second, and third driving units, the first, second, and third stators can be of an integrated structure. In such a case, the reaction force acting on the base when driving the first, second, and third stages can be made to be a force acting on the same plane.
According to the second aspect of the present invention, there is provided an exposure apparatus to transfer a predetermined pattern onto a substrate by exposing the substrate with an energy beam, the exposure apparatus comprising a stage device according to the present invention as a substrate stage device to hold the substrate.
With this apparatus, the pattern is transferred onto the substrate while the substrate is held and moved by the stage device in the present invention. Therefore, deformation and vibrations of the exposure apparatus that occur when the center of gravity of the stage device shifts can be prevented while meeting the requirements for large-sized substrates. Accordingly, the throughput can be improved while improving the precision of pattern transfer. Also, since the substrates can be respectively held and moved independently on the first and second stages of the stage device of the present invention, two substrates can be concurrently processed with the exposure apparatus, thus improving the throughput.
The exposure apparatus of the present invention can have the structure of further comprising: an exposure main body portion to transfer the predetermined pattern by irradiating one of a first and second substrate held on the first and second stage with the energy beam on exposure; an alignment portion to detect array coordinates of a divided area formed on a surface of a remaining of the first and second substrate; a first position detection device to detect a position of the first stage; and a second position detection device to detect a position of the second stage, and the one of the first and second stage is positioned to a transferring position of the predetermined pattern, and the remaining of the first and second stages is positioned with respect to the alignment portion. In such a case, the exposure apparatus can perform the exposure process on the first substrate, while concurrently performing the alignment process of detecting the array coordinates of a divided area formed on the surface of the other substrate. In the exposure process, one substrate is positioned with respect to the main body portion for exposure based on the detection result of the first stage position obtained by the first position detection device, and the pattern is transferred. Meanwhile, in the alignment process, the other remaining substrate is positioned with respect to the alignment portion to detect the arrangement coordinates of the divided areas formed on the surface of the substrate, based on the detection result of the second stage position obtained by the second position detection device. Accordingly, the throughput of the exposure apparatus can be greatly improved while improving the precision of the pattern transfer.
It is preferable for the exposure apparatus to further comprise a detection device to detect the positions of the moving members of the stage device. In such a case, the shift in the center of gravity of the stage device can be accurately canceled out. Also, if the controlled variable to drive the moving members change in accordance with their position, by controlling and driving the moving members based on their position, they can be driven in a desired form.
In this case, the first position detection device can be structured so as to comprise: a first optical member fixed to the first stage; and a first interferometer system to detect the position of the first stage by irradiating the first optical member with light and receiving reflected light from the first optical member, and the second position detection device can comprise: a second optical member fixed to the second stage; and a second interferometer system to detect the position of the second stage by irradiating the second optical member with light and receiving reflected light from the second optical member. In such a case, the position of the first stage (i.e., the position of the first substrate) and the position of the second stage (i.e., the position of the second substrate) can be detected with extreme accuracy by the first and second interferometer systems. This makes it possible to transfer a pattern with high precision.
An interferometer system is preferably used, also to detect the position of the moving members. In such a case, the shift in the center of gravity can be canceled out very accurately. Also, if the controlled variable to drive the moving members change in accordance with their position, by controlling and driving the moving members based on their position, the moving members can be driven with an extremely high accuracy.
In the exposure apparatus of the present invention, the exposure main body portion can be structured to comprise: a mask stage device to hold and move a mask on which the predetermined pattern is formed and which is irradiated with the energy beam; and a projection optical system to image-form the predetermined pattern with the energy beam via the mask. In such a case, the pattern formed on the mask can be transferred onto the substrate with higher precision and throughput.
The mask stage device can be structured to comprise: a mask stage to hold and move the mask; and a mask stage base which movably holds the mask stage, the mask stage base moves by a reaction force generated when the mask stage moves. In this case, the movement of the mask stage base cancels out the shift in the center of gravity of the mask stage device when the mask stage moves to move a mask. Accordingly, this prevents deformation and vibration of the exposure apparatus when a mask is moved, and allows the mask to be moved at a high speed. Thus, the pattern formed on the mask can be transferred onto the substrate with a higher precision and throughput.
According to the third aspect of the present invention, there is provided a scanning exposure apparatus comprising: a mask stage device which has a fine adjustment stage and a coarse adjustment stage to hold a mask, the stage device moves the mask; a substrate stage device which is separated from the coarse adjustment stage and include a first substrate stage to hold and move a first substrate, and a second substrate stage to hold and move a second substrate, and a projection optical system which is separated from the coarse adjustment stage and the substrate stage device and projects a pattern of the mask onto one of the first and second substrate stage.
According to this apparatus, the mask on the mask stage device and one of the first and second substrates are synchronously moved while the mask is irradiated with an exposure beam. In this case, the mask is moved by the mask stage, whereas, one of the first and second substrates is moved by the substrate stage device. Such movement of the mask and substrate can cause reaction force from the driving force, which may affect other portions of the exposure apparatus in the form of vibrations. Or, it can cause the center of gravity of the mask stage and substrate stage to move, which in turn may cause a deformation of the apparatus. However, the coarse adjustment stage, the substrate stage device, and the projection optical system are arranged separately from one another, and are substantially free from the influence of vibrations or the like when the mask or substrate are driven at other portions. Consequently, patterns can be transferred with high precision. Also, since this apparatus has two substrate stages, i.e., the first substrate stage and the second substrate stage, various processes can be performed concurrently on the two substrates, thus improving the throughput in exposure.
With the scanning exposure apparatus of the present invention, the apparatus can have the structure of further comprising a substrate stage reaction force suppressing device to suppress a reaction force generated when at least one of the first and second stage moves. In such a case, vibration caused by the reaction force due to the movement of at least one of the first and second substrate stages can be suppressed, and kept from traveling to other portions of the exposure apparatus, therefore the pattern can be transferred with high precision.
With the scanning exposure apparatus of the present invention, the apparatus can have the structure of further comprising a suppressing device to keep a center of gravity of the substrate stage from moving which occurs when at least one of the first and second stage moves. In such a case, deformation or vibration due to the shift in the center of gravity of the substrate stage device caused by the reaction force generated when at least one of the first and second substrate stages moves can be suppressed, thus the pattern can be transferred with high precision.
According to the scanning exposure apparatus of the present invention, it can have the structure of further comprising a mask stage reaction force processing device to suppress a reaction force generated when at least one the fine adjustment stage and the coarse adjustment stage moves. In such a case, vibration caused by the reaction force generated when at least one of the fine adjustment stage and coarse adjustment stage moves can be suppressed from travelling to other portions of the exposure apparatus, therefore, the pattern can be transferred with high precision.
According to the scanning exposure apparatus of the present invention, it can have the structure of further comprising a suppressing device to keep a center of gravity of the mask stage device moving which occurs when at least one of the fine alignment stage and the coarse adjustment stage moves. In such a case, deformation or vibration due to the shift in the center of gravity of the mask stage device caused by the reaction force generated when at least one of the fine adjustment stage and coarse adjustment stage moves can be suppressed. The pattern, therefore, can be transferred with high precision.
The scanning exposure apparatus of the present invention can have the structure of further comprising a fine adjustment stage driving unit which is arranged between the fine adjustment stage and the coarse adjustment stage, the driving unit drives the fine adjustment stage. In such a case, the reaction force caused when driving the fine adjustment stage by the fine adjustment stage driving unit act on the coarse adjustment stage. However, since the coarse adjustment stage is separated from the substrate stage device and the projection optical system, vibration and the like caused by the reaction force acting on the coarse adjustment stage can be suppressed from travelling to the substrate stage device and projection optical system. Also, by adjusting the position of the fine adjustment stage the position of the mask is accurately controlled. Therefore, the pattern can be transferred with high precision.
With the scanning exposure apparatus of the present invention, it can have the structure of further comprising: a first alignment device to perform alignment of the first substrate; and a second alignment device to perform alignment of the second substrate. In such a case, while one substrate is held on one of the first and second substrate stages and subject to scanning exposure with an exposure beam through the projection optical system on scanning exposure, the other substrate held on the other substrate stage can be aligned. That is, scanning exposure of one substrate and alignment of the other substrate can be concurrently performed. Accordingly, the throughput of substrate exposure can be improved to, around double, at a maximum.
This apparatus can have the structure of further comprising a holding member to hold the projection optical system, the first alignment device, and the second alignment device. In such a case, as with the projection optical system, since the first and second alignment devices are separated from the coarse adjustment stage and substrate stage device, these devices are substantially free from the influence of vibration caused when the mask or the substrate is moved. This, therefore, makes it possible to perform alignment and pattern transfer with high precision.